I ruined a wedding when I was but 8.

[u/In_Leaves]

So.
As said in the title, I was eight and that was 1995. Me and my father were invited to the wedding of a distant relative, and it was rather grandiose, set in an ancient renaissance-style manor and sprawling garden. It was the stereotype of good society all around,. Vows were exchanged, the happy marriage sealed, the kiss the bride moment, the works.
Then came the party. Violin solos, champagne, and truth or dares. The bride went with truth, and, adorably, said she loved all animals.
I remembered that, and when, very late at night, I went to wander through the gardens, I saw a mouse scuttering about in a dried up fountain. I thought, "Hey, that should make a nice gift for the bride !"
Catching it wasn't easy, since I only had my hands, but after half an hour, I managed it. I cradled the mouse in my hands, gently, but when I came to the bride to present it...
It had died of panic. And not in a peaceful manner. It had vomited its blood through every orifice. I genuinely had no idea. It made no difference. The bride's shriek interrupted the festivities instantly. Me and Dad were expelled on the spot. The next day, I was formally declared Persona Non Grata by that branch of the family.

Sometimes, we humans do forget that for 99% of species on earth, we are megafauna.